Welding products that promote the formation of graphite in the weld deposit are currently used for all types of cast irons. Formation of graphite in the weld deposit provides the advantages of 1) causing a volume expansion that offsets shrinkage stresses developed by solidification, 2) forming chip-breakers to facilitate machining of normally "gummy" nickel-containing alloy deposits and 3) forming graphite at the expense of carbides to reduce the tendency for cracking in the deposit caused by the formation of very hard, brittle carbides.
Generally, increasing the size and volume fraction of carbides in a cast iron weld deposit increases the cracking tendency of the weld deposit. Virtually all cast iron welding products on the market today employ graphite-forming technology to provide the benefits of graphite phase and minimize cracking. In addition, aluminum and silicon are often added to weld metals to enhance oxidation resistance. Aluminum and silicon further serve as graphite phase stabilizers in iron castings.
It has been discovered that when ductile iron is welded to aluminized steel with conventional graphite forming nickel-iron products, the weld has poor high temperature properties. At high temperatures graphite migrates to grain boundaries and weld centerlines to form areas of weakness. At temperatures of approximately 500.degree. to 800.degree. C., graphite-containing welds to cast iron products quickly fail.
It is an object of this invention to provide a weld deposit that will not fail at elevated temperatures.
It is a further object of the invention to provide a flux-cored welding wire or flux coated electrodes capable of welding cast iron for high temperature applications.
It is a further object of the invention to provide a filler metal capable of welding cast iron for high temperature applications.
It is a further object of the invention to provide a welding material capable of welding aluminized steel to cast iron for high temperature applications.